A £1 billion European space telescope to be launched in 2024 raises the real prospect of finding an alien civilisation among the stars, it is claimed.

Astronomer Don Pollacco, heading a consortium of scientists involved in the Plato mission, believes such a momentous discovery could happen in the next 15 years.

Signs of pollution in an Earth-like planet's atmosphere would indicate the existence of an industrial society - and alter our world view for ever.

"There are certain things you would not expect to occur naturally, and pollution is the obvious one," said Dr Pollacco, from the University of Warwick.

"I'm talking about various kinds of metals that would not occur in that state in that atmosphere. You would have to interpret that as a sign of some kind of civilisation.

"We could do this in our lifetime; that's the most exciting thing. It would change everything. It would be amazing."

The Plato (Planetary Transits and Oscillations of stars) space telescope will prepare the way for scientists searching for alien life by locating the first genuinely Earth-like exoplanets orbiting nearby stars.

Given the enormous age and size of the universe, the chances of stumbling on an extra-terrestrial industrial society in our cosmic backyard might be slim, but Dr Pollacco insists it cannot be ruled out.

"For a long time a lot of us have been driven on by that sort of idea," he said.

The European Space Agency (Esa) today announced that Plato had been selected as part of its 2015-2025 Cosmic Vision programme.

It will break new ground in astronomy by using a "bug eye" array of 34 individual telescopes to search for planets among up to a million stars.

Operating like the compound eye of an insect, the observatory will have a field of view 20 times greater than that of the American space agency's hugely successful Kepler space telescope. Kepler has already discovered 4,000 candidate and confirmed extra-solar planets.

Plato will monitor relatively nearby stars searching for tiny dips in their brightness as orbiting planets move in front of them.

It will also probe seismic activity in the host stars, providing valuable data on their age.

The telescope's measurements will make it possible to analyse the composition of extra-solar planets in a way that has not been achieved before.

It will enable astronomers to distinguish between Earth-sized planets or "super-Earths" that are light and gassy, like Neptune, or heavy and rocky like the Earth.

A rocky Earth-sized world with an iron core in a star's "habitable zone" - the orbital path where temperatures are mild enough to allow liquid surface water - would stand the best chance of harbouring evolved forms of life.

"Plato will allow the first systematic survey of nearby planets for indications from advanced life forms, as well as 'slime'," said Dr Pollacco. "A few years ago this would have been science fiction, and now it's coming to pass as science fact."

The telescope will pave the way for other missions, providing a shortlist of the most promising candidate worlds whose atmospheres can be studied.

Nasa's James Webb telescope, due for launch in 2018, will have the ability to "sniff out" exoplanets by analysing starlight filtering through their atmospheres.

Plato will be launched on a Soyuz rocket from Esa's Kourou spaceport in French Guiana on a mission lasting an initial six years.

It will occupy a fixed position in space at the L2 Lagrangian Point, where the gravitational pull of the Sun and Earth cancel each other out.

Focusing on some of the brightest and nearest stars, the telescope is expected to discover and characterise thousands of new planets.

Each of its 34 "eyes" has an aperture of 12cm, and Plato will be equipped with the largest camera sensor ever flown in space. Its 136 charge-coupled devices (CCDs) have a combined area of almost a square metre.

Heike Rauer, from the German Aerospace Centre in Berlin, who will head the overall mission, said: "Plato will enable us to find planets that orbit their star in the habitable zone, where liquid water is expected and where life as we know it can be maintained.

"In the last 20 years more than 1,000 exoplanets have been discovered, with quite a few planetary systems among them. But almost all of these systems differ significantly from our Solar System in their properties, because they are the easiest-to-find examples.

"Plato firmly will establish whether systems like our own Solar System, and planets like our own Earth, are common in the galaxy."

The telescope is expected to cost Esa just under £500 million, but with hardware contributions from member states the total price tag is likely to reach around £800 million.